ADD-ONS / SCALES
Muscle strength testing (Oxford scale)
David Goldemund M.D.
Updated on 29/12/2023, published on 16/12/2023
- muscle strength testing is typically performed as part of a physical examination; it may provide information about neurological deficits.
- it may be referred to as motor testing, muscle strength grading, manual muscle testing, or any other synonyms
- it is used to quantify the weakness and can be effective in differentiating true weakness from imbalance or poor endurance
- strength depends on a combination of morphological and neural factors, including muscle cross-sectional area and architecture, muscle-tendon stiffness, motor unit recruitment, rate coding, motor unit synchronization, and neuromuscular inhibition
- in the Oxford Scale, which is the most commonly used, the patient’s strength is rated on a scale of 0 to 5 by testing key muscles in the upper and lower extremities against the examiner’s resistance
- typical muscles tested include:
- shoulder abductors
- elbow flexors
- elbow extensors
- wrist extensors
- finger flexors
- hip flexors
- knee extensors
- dorsiflexors
- great toe extensor
- plantar flexors
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No muscle activation
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Trace muscle activation, such as a twitch, without achieving full range of motion
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Muscle activation with gravity eliminated, achieving full range of motion
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Muscle activation against gravity, full range of motion
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Muscle activation against some resistance, full range of motion
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Muscle activation against examiner’s full resistance, full range of motion
Limitations of the grading scale
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muscle tested may have no clinical relevance; it is practical to add functional testing
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non-linearity (the difference between grades 3 and 4 is not necessarily the same as the difference between grades 4 and 5)
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inter-rater reliability
- fluctuating performance (fatigue, cooperation)
Functional testing
Functional testing typically involves assessing an individual’s ability to perform activities that reflect their muscular strength and endurance in real-life situations
- grip strength test – measures the maximum isometric strength of the hand and forearm muscles (dynamometer may be used)
- sit-to-stand test – assesses lower body strength by counting how many times a person can stand from a sitting position in a given time frame
- squat test – assesses lower body strength by counting the number of squats a person can perform.
- walking on the heels and on tiptoe tests distal strength
- timed up and go (TUG) Test
- a simple and commonly used test to assess a person’s mobility, balance, walking ability, and risk of falling
- the individual sits in a chair with their back against the back of the chair
- on the command “Go,” the individual stands up from the chair, walks to a marker 3 meters away, turns around, walks back to the chair, and sits down again
- the time is measured from the start command until the individual is seated again
- in general, a time of less than 10 seconds is considered normal for healthy older adults. Times longer than 12 seconds may indicate mobility issues and an increased risk of falling
- 6-minute walk test (6MWT) – measures the distance a person can walk quickly on a flat, hard surface in six minutes, reflecting endurance
- functional reach test
- the individual leans forward as far as possible, keeping their feet fixed on the ground. The distance between the start and end position of the fingertip is measured
- the average reach distance for healthy adults is typically ~ 10 inches/25 cm; a shorter reach distance may indicate balance problems
Dynamometer
- distal strength can be measured semiquantitatively using a handgrip ergometer (or an inflated blood pressure cuff squeezed by the patient) to record grip strength
- requires specialized equipment, most commonly a dynamometer, which enables more precise measurement of the force that a muscle can exert and can record changes in strength over time
